Currently, most operators need to maintain two separated charging systems, i.e. an IT based postpaid charging system and an intelligent-networks based prepaid charging system. The postpaid charging system employs an offline charging manner, and it periodically collects Call Detail Records (CDRs) over network, determines the expense for a call according to the information (e.g. the call duration for a user, caller information, callee information, position information, etc.) included in the call detail record, and determines the tariff based on the call detail record after the call. Therefore it is impossible to achieve a real-time control for a user's call. The prepaid charging system employs an online charging manner, and it determines in real time a duration for a user to make a call in accordance with the balance of the user's account. When the user runs out of the balance of his account, the call will be cut off immediately. The prepaid charging system needs to monitor and control the call of the user in real time.
For an operator, maintaining two charging systems means a high cost and furthermore some functionalities of one system cannot be implemented or cannot be implemented well in the other system. For example, re-rating is a functionality of the postpaid charging system, which can re-rate the expense for the call detail record in accordance with changes of the service price. However, it is difficult for the real-time prepaid charging system to realize re-rating because the prepaid charging system needs to monitor a user's call request in real time and to update the user's account profile in real time and cannot make recalculation on the user's account profile as if it was rolled back to a previous stage. Specifically, for the prepaid charging system, before each call is established, the system will read the user's account profile, and if the account profile is updated at this time, it is impossible for the system to read the current account profile for the current call request or read a wrong account profile.
More and more operators and market analyzers recognize that a charging system converging both the postpaid charging system and the prepaid charging system will be the future developing trend, and such a converged charging system not only can reduce the cost but also can provide users with blended services. Most operators urgently demand such converged charging system provided by the vendors.
However, as stated above, re-rating is a functionality of the postpaid charging system and it is difficult to be implemented in the prepaid charging system. How to implement the re-rating function for the converged charging system will be a challenge. Thus, an approach to implement the re-rating function for the prepaid charging system is needed.